JPH0422332B2 - - Google Patents

Abstract

PURPOSE:To secure a good bonding property of the lead to the fine metal wire by a method wherein, during the process of bonding of the fine metal wire and the lead, the bonding areas of the lead are locally heated and are softened. CONSTITUTION:A copper alloy lead 4 and a semiconductor chip 2 are placed on a hot plate 6 at 250 deg.C or thereabouts. In that state, the electrode 3 of the semiconductor chip 2 is connected with the bonding areas of the copper alloy lead 4 using a copper wire 1 by an ultrasonic wave combined thermocompression bonding system, for example, yet during the bonding process, a laser beam 8 is irradiated on the back surfaces of the bonding areas of the copper alloy lead 4 from the lower side of the hot plate 6 and the bonding areas are heated over a temperature range of 260 deg.C-1,000 deg.C. Moreover, by forming the hardness of the lead into one of Hv 50-100 in the Vickers hardness, the bonding property of the lead to the fine metal wire is significantly improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, particularly in the manufacturing process of an IC, a transistor, etc.
The present invention relates to a wire bonding method for connecting electrodes on a semiconductor chip and lead terminals using thin metal wires.

[Conventional technology]

Conventionally, in this type of semiconductor device, gold has been used as the wire material, and the lead surface has been subjected to surface treatment such as silver plating. FIG. 4 shows a schematic external view of a semiconductor device configured in a conventional manner. In the figure, 1 is a metal wire, 2 is a semiconductor chip, 3 is an aluminum electrode formed on the surface of the semiconductor chip 2, 4 is a copper alloy lead, 5 is a silver plating layer formed on the surface of the lead 4, The above wire 1 is attached to the electrode 3 mainly by thermo-compression bonding method combined with ultrasonic waves.
and is joined to the lead 4.

[Problem that the invention seeks to solve]

Here, from the viewpoint of reducing material costs and improving long-term reliability of the device, the wire 1 material was replaced with copper from gold, the silver plating layer 5 on the surface of the lead 4 material was omitted, and the copper wire 1 was directly placed on the lead 4. It is possible to join them.

In addition, in ultrasonic thermocompression bonding,
In order to obtain a good bonding condition, it is necessary to sufficiently destroy and remove adsorbed materials such as oxide films on the material surfaces, and to expand the contact area between the new surfaces after the oxide film is destroyed by plastic deformation of the materials at the bonding interface. It is extremely important to do so.

However, when the silver plating layer 5 is omitted and bonding is performed directly to the copper alloy lead 4, the above 2.
Compared with conventional silver-plated leads, it is extremely difficult to obtain good results in terms of both the removal of the oxide film and the plastic deformation at the bonding interface.
Therefore, when bonding to the lead 4, a bonding failure occurs, that is, insufficient bonding strength, and in extreme cases, peeling occurs during bonding.

One possible way to solve this problem is to set the ultrasonic output, that is, the vibration amplitude, in the bonding process described above to be larger than that for conventional gold, but this method does not allow sufficient bonding. If strength is to be obtained, the copper wire may be deformed too much during bonding, resulting in a decrease in the strength of the copper wire itself.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device that can ensure good bonding between a thin metal wire and a lead.

[Means for solving problems]

In the method for manufacturing a semiconductor device according to the present invention, the bonding area of the lead is locally heated and softened during the step of bonding the lead to the thin metal wire.

[Effect]

In this invention, during the bonding process,
Since the bonding area of the lead is locally heated and softened, the plastic deformation of the bonding area of the lead is improved while maintaining sufficient mechanical strength of the lead, allowing contact between the fine metal wire and the lead over a large area. It is to be joined in this state.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 schematically show a method for manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. For example, a hot plate of about 250° C., 7 a laser gun such as a YAG laser or an argon laser, 8 a laser beam, and 9 a capillary chip which is a bonding tool.

In the method of this embodiment, as in the conventional method,
The leads 4 and the semiconductor chip 2 are placed on a hot plate 6 at around 250°C, and in that state, the electrodes 3 of the semiconductor chip 2 and the bonding area of the copper alloy leads 4 are bonded using, for example, a thermocompression bonding method combined with ultrasonic waves. The copper alloy lead 4 is connected from the bottom of the hot plate 6 during the bonding process.
A laser beam 8 is irradiated onto the back surface of the bonding area to heat it to a temperature range of 260°C to 1000°C.

Copper alloy lead 4 has metal elements added to it to ensure its mechanical strength, and has undergone work hardening history, so it has a relatively high hardness compared to copper wire 1, and is hard to maintain as it is. It is difficult to plastically deform during bonding, so the laser beam 8 is connected to the copper alloy lead 4.
By irradiating the back surface of the bonding area, only the bonding area is locally softened while maintaining sufficient mechanical strength for the lead 4.

Figure 2 shows the relationship between lead hardness and bonding strength obtained through experiments, and shows that bonding performance can be significantly improved by setting the lead hardness to Hv50 to 100 in terms of Vickers hardness. I understand. In addition, in the figure, a
indicates the passing strength, that is, the required bonding strength.

In the method of this embodiment as described above, by locally reducing the hardness of the lead, it is possible to greatly improve the bondability of the copper wire to the copper alloy lead without silver plating. It is possible to achieve a significant reduction in the amount of precious metal materials used such as.

Further, FIG. 3 schematically shows another embodiment of the present invention. In the figure, the same reference numerals as in FIG.
The hot plate 11 is a second hot plate that heats the leads 4 at a high temperature, for example, in a temperature range of 260°C to 800°C.

In the method of this example, during the bonding process,
First hot plate 1 for heating semiconductor chip 2
The lead 4 is heated to a temperature range of 260 DEG C. to 800 DEG C. by a second hot plate 11 provided separately from the lead 4.

In addition, although the above embodiment shows an example of application to a copper alloy lead, the same effect can be obtained when applied to an iron-based lead or the like. Further, the metal thin wire may be a copper alloy thin wire instead of a copper wire.

〔Effect of the invention〕

As described above, according to the method for manufacturing a semiconductor device according to the present invention, the bonding area of the lead is locally heated during the bonding process between the lead and the lead. This has the effect of ensuring good bonding properties and significantly reducing the amount of precious metal materials used.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between lead hardness and bonding strength, and FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the conventional method. 1... Copper wire (metal thin wire), 2... Semiconductor chip,
3... Electrode, 4... Copper alloy lead, 8... Laser beam, 11... Hot plate. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device in which an electrode on a semiconductor chip and a lead are connected using a thin metal wire, characterized by locally heating and softening the bonding area of the lead during the wire bonding process. A method for manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the lead is made of a copper alloy or an iron alloy. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the thin metal wire is made of copper or a copper alloy. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the back surface of the bonding area of the lead is irradiated with a laser beam. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the lead is heated by a hot plate. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the hardness of the bonding area of the lead is locally tempered to a range of 50 to 100 in terms of micro-Vickers hardness.